Friday, February 8, 2019

2019 ~ Building SSB Transceivers

The Building of a SSB Transceiver ~ You can do it!

2/21/2019 ~ Go Daddy Now Fixed! The audio Amp Schematic is on the website.

2/20/2019 ~ Problems with Go Daddy!!

For over 24 hours I have been trying to upload updated schematics and information to my n6qw website. It seems like Go Daddy who hosts my website has some sort of issue with a windows server. One solution that offered was for me to spend more money and move over to a Linux server OR just wait until they get around to fixing the problem. Not only is it a cost issue but also I would have to start from scratch and rebuild all five of my websites. This makes about as much sense as declaring an emergency so the emperor can have his wall.

My alternative is to wait a bit longer to see if they can resolve the problem or just post the info here. Here is one of the updated schematics. Perhaps if any of you have a Go Daddy account you may have the same problem.

Pete N6QW

2/18/2019 ~ Toroids are not self shielding!

I noted that after installing the shield on the left hand side there appeared to be a detuning of the band pass filter. Despite what many have said toroids are not necessarily self shielding.

When I installed the side piece, I thought there was a sufficient space gap between the steel based side panel and the T-68-2 cores. There was not and so the BPF was being detuned. There just was no way with the side panel in place to re-peak the BPF to the proper value unless I followed the practice espoused by Ian Roussel (Full Custom Garage on the Motor Trend Channel) which is make a hole.. The "A" change was to cut about a 1 and 1/8 inch round hole in the side panel stiffener right over the BPF. This accomplished two things. Firstly it reduced the effects of the steel on the BPF and secondly to provide access to the trimmer caps so that the BPF can be tuned with the steel side piece in place. Worked perfectly -- the hole does not affect the stiff properties of the side bracket. We are good to go. The 2nd photo below shows the side piece without the access hole. You have got to love when a plan comes together!

Pete N6QW

2/17/2019 ~ Be sure to visit www.n6qw.com where the project is documented and new schematics have been added over the past two days. Learning to Hem ~ No we are not sewing!!!

In keeping with trying to use stuff I already have knocking about the shack we now address a common problem with homebrew construction: making or buying a case enclosure. The problem is compounded by the fact the front panel is from the former 30M CW transceiver project that was a QRP Quarterly article. But the back panel came from a transceiver that was rebuilt at least three times.

Now for the disconnect. The front panel is 4 inches high and the back panel a mere two inches. Standing alone the front panel flexes as you spin the encoder --not a good plan. Thus to stiffen things we need to connect the front panel to the back panel to add rigidity. We essentially have a trapezoid and how to fabricate those two pieces, one for each side, and not spend a fortune on material.

One of my currently favorite TV shows is the Velocity Channel (now Motor Trend) and my new hero is Ian Roussel of Full Custom Garage. This guy uses what is at hand and often comes up with very creative solutions. In one episode he needed a round metal structure to house the odometer that was being affixed to a new dashboard. He spotted his dog's water bowl which it turned out was stainless steel and just the right size. The poor dog now drinks out of a plastic dish. But it is that sort of thinking we need to employ when we fabricate our homebrew rigs.

A trip to Home Depot yielded a piece of galvanized metal flashing that was about 8 X 11 inches. The price was $1.14 and was enough material to make two sides. But wait you are thinking that stuff is awful flimsy. True; but if you bend it over along one of the seams --it becomes rigid. A pair of Tin Snips, a metal straight edge with scribe and a bench vise is all that is needed to make these very durable side braces. The galvanized metal can be soldered as well as painted. Thus the bending over and doubling is known in the fabrication world as "hemming".

The first item on the list should be a manila folder that will serve as a pattern to overlay on the sheet metal and provides a template to scribe the outline. Keep in mind you have right and left hand pieces and thus you must flip the pattern over to draw the scribe lines for the different sides. The 1st photo below shows the template of the sides and you can see the bend line for the hemming. On either end add 1/2 inch of material that is bent over and will provide the anchor points to the front and back panel.

You might have to "play a bit" with the metal bending so get two sheets of the material. The finished rig is a far cry from the boards screwed down to work bench as it was initially built. Nice looking Rig, Pete!

Ian Roussel would be proud.

Pete N6QW

2/15/2019

2/13/2019

[2/11/2019 I have started publishing schematics for the Simple SSB on my website at www.n6qw.com. Although it is doubtful that many (if any) would take up the fabricating of this rig, there just may be one or two who have an interest.]

Just the other day I was having a very nice QSO with Gene W6QFU and we exchanged our station line up. W6QFU is lucky in that he just recently acquired a very nice ICOM 7300 and has joined the ranks of perhaps over 100,000 other hams world wide who now have that rig sitting at the operating position. Some would suggest it is an appliance rig; but at the same time it is a great sounding rig that undoubtedly is very popular and the current price point puts it in reach of many hams. Guess there is a link to price point and the numbers in shacks around the world.

On my end --yes, yet another new rig just finished and W6QFU was the third contact on that rig. So I was anxious to see how it held up. Well I might add...ARRL as previously reported will start a new podcast one month from now called "So What Now?" A possible answer to that question (or perhaps it is a challenge) is to suggest you build your own SSB transceiver. Trust me what I am suggesting you build is not in the ICOM 7300 class; BUT it puts out a respectable signal with a rock solid frequency stability and it is something you built and can be built for about $100. [YMMV depending on how much junk you have in the junk box.]

But let us go back in time to review SSB transceivers starting in the late 1950's and early 1960's. BOOM there was an explosion of technology in that time frame starting with the Collins KWM-1 and KWM-2 (the cost --read a years salary for most middle class working folk) to more modest rigs that were less costly. Heathkit did much for the hobby in offering single band transceivers that could be had for about $100. I remember being on Midway island (actually two island Sand and Eastern Island) in 1963 where a fellow Navy ham on Eastern ran one of those rigs into a 13 dB gain Rhombic antenna pointed at the US. Everyone wanted to talk to him--firstly he was DX and secondly that gain antenna took that 100 watts and made it look like more than a KW (like 2KW and you can check the math [10*log(2000/100) = 13dB]) But even the simple Heathkit rigs involved some pretty complex circuitry to receive and transmit a signal using common circuit elements.

There were many complicating factors in building a homebrew SSB rig in the 1950's and 1960's

Socketry --yes you had to do all of that metal bashing and mechanical engineering to layout all of the tubes and components that had to be affixed to a large aluminum chassis

Power Supplies. You often required Filament, Bias, LV, HV and control power to operate the rig. We are indeed fortunate --12 VDC and we are there today

Front panel controls abound as does a space reservation for the Analog Dial Readout

So there was much involved aside from just a few schematics.In todays rigs none of those issues exist as many circuit elements simply solder to a few pads. Socketry is minimized so you can feel secure in selling your set of Greenlee Chassis Punches at the next block yard sale. You won't need them. A 12 VDC well regulated supply or even batteries can run your rig. You only need to cut out a rectangular hole in the front panel for your favorite display (LCD or Color TFT). If it is a touch screen then that will reduce further the number of controls needed

Fast forward to today some 60 years later and building a transceiver is much easier and uses far less components thanks to IC's, PLL's and inexpensive commercial crystal filters. Let me take a moment to discourage the use of homebrew crystal filters especially if you have not previously built one, and two if you lack some pretty decent test gear. Sure you can purchase crystals inexpensively but that is only 5% of the task. So reject all of those claims that you only have to buy 5 crystals at 40 cents a piece and you are there --you aren't! INRAD sells a nice 4 pole 9 MHz experimenter's filter for about $30 and you can also buy 9 MHz filters from the GQRP club for about the same shipped to you. Yes I do have several rigs with homebrew crystal filters so I do speak with experience. But it is a simple decision if you do not have that experience --buy the filter!So lets talk a minute about the SSB transceiver architecture. and we'll proceed first to the block diagram.

Many rigs today are bilateral or as some prefer bi-directional in that a) signals can be routed in two directions through the circuit element and b) because of (a) you can use that circuit element in both transmit and receive.Here is an example of one circuit element that I frequently use... a bidirectional IF Amplifier Module as shown above. This module has four transistors, a bunch of caps and resistors, two matching broadband transformers, a crystal filter and a relay to bias parts of the circuit to change the signal direction. The common 2N3904 and 2N3906 make up one amplifier stage and following the crystal is a second identical stage. The amplifier circuit was invented by Plessy and appears in EMRFD (just so it has street creds). Here is what is happening .. with one bias condition the two 2N3904's take on the amplifier role. With the alternate bias condition the 2N3906's are doing the heavy lifting. This circuit is good up to about the 6 Meter band and a single amp pair is good for 15 to 17 dB of gain. Here are some notable items. This is a broad band circuit --there are no IF transformers and there is nothing to peak or tweak. The resistor compliment for a single amp stage is 22 Ohms, 2 X 100 Ohms,. 2X 680 and a 1K. For caps -- six each 100 Nano Farad. The power source is actually 6 VDC but I run mine on 8 VDC through a three terminal regulator. Add in two FT-37-43 matching transformers [19 Turns solenoid wound tapped a 6 turns. The 19 turns squared is 361 and the 6 turns squared is 36 --thus 361/36 = 10. So this transformer matches the 50 Ohms of the Plessy to the 500 ohms on the GQRP filter.]Including the Linear Amp control ( another 2N3904) there are eleven transistors and FET's along with two packaged ADE-1 Double Balanced Mixer's an Arduino Uno R3 (because it was in the junk box) a 16X4 Seasick Green LCD (also a junk box refugee). BTW I was looking at some 16x4 Blue White LCD's --$8 shipped from the USA. Lest I forget the GQRP 9 MHz crystal filter. If you use the INRAD it is a 4:1 match as the INRAD's are 200 Ohms.This may be a good place to stop for now… but to whet your whistle:

Interesting note this front panel was cut out of the front panel that was used for the 30 Meter CW transceiver that originally was a QRP Quarterly article. I should tell you that I was encouraged by QRP Quarterly to design and build this CW rig so it would appeal to those QRPer's who dominate CW. I did as was suggested and did make one contact to prove it works . The rig then went into the never to use again and possible use in other projects bin. There it has sat for five years. Now is the time to use it!The panel was reversed as it was double sided PCB. The Key is now the Mic jack and where the analog dial was --it was cut out for the LCD. The audio amp stage was cut out of the original main board. There are three empty holes in the new panel. Above the red knob the audio gain control will be installed and the hole in the lower right hand corner will house the audio output jack. and the small hole next to the mic jack will be filled with a bolt and nut. The original panel was 8 inches long and with a bit of juggling and cutting material off of each end the size is now 6 inches wide. Thank you Velocity Channel for giving me some really great ideas! Yes Virginia having a CNC sure makes life a lot easier when you are fabricating radios. The part that was cut off included the former part containing the volume control and headphone jack. The two bolt holes nearest those were enlarged to house one of the toggle switches and the new headphone jack. New panel controls include MOX and TUNE button (red button), Volume control, Main Tuning, USB / LSB Select and VFOA / VFOB Select, Microphone Jack and Headphone Jack. Lest I forget the 16X4 LCD.

Below is the rig screwed down to the top of the work bench. In the very bottom is the IF module, Audio amp and Microphone amp. To the left of the IF module is the BPF and above the IF the bidirectional J310 amp and the single 2N2219 feeding the IRF510. To the right of the IRF510 and the microphone amp is the LPF. The junk in the center is my power buss and some relays used for TR. The RCA plug/cord above the J310's is the linear amp control. The "T" line feeds a 1K resistor into the Base of a 2N3904 with the Emitter grounded at the collector goes to the control line in the follow on linear amp. Take a good look --aside from looking like crap --there are not many parts. I did use it on WSPR and FT8 as well as a few SSB contacts. the future work will involve some packaging to sanitize the look. !

It is a shame that many hams think building a rig is too difficult. Drop me a comment if you would like to see more detail on this project. Oh should mention portions of the design are LT Spice simulations so there is solid science behind the modules. These include the BPF, LPF, the J310 Bi-Directional amp, the 2N2219 driver stage and the microphone amp circuit. Oh --the mic amp design is now the same design used in the audio pre-amp stage. The circuits not simulated are the Plessy amps (from EMRFD) and audio final stage LM386 and the IRF510. I was asked a question about how the Simple Transceiver compared to the Sudden Transceiver Project. There are two areas of comparison the first of which is performance and the second the circuit elements themselves. Performance is equal and thus I am pleased; but the circuit elements do differ and the following explains the differences.

There is some circuits which are alike and some not so. Physically the Sudden is a
smaller footprint. Some circuit differences include:

The IF Module uses the
Plessy amps and external DBM’s. The Sudden using the NE602 provides the mixer
stage and the balanced modulator on the input side and the mixer and product
detector on the output side. The LO & BFO are switched whereas in the Simple SSB rig they feed the same DBM regardless of T or R. The Sudden is a
single pass whereas the Simple is bidirectional.

The simple SSB takes the
pre-driver used in the Sudden and makes it bi-directional so it is the Rx
RF Amp on receive and Tx pre-driver on transmit. The Sudden has a separate Rx RF Amplifier stage

Only one BPF versus two in the Sudden

The Driver and Linear
Amp are the same

The Mic Amp is the same
but the Audio Amp different

The Sudden uses a Color
TFT and Nano and the Simple the Uno R3 and the 16X4 LCD

The LPF’s are the same.

Bottom line ~ not a lot of parts! For those who wonder this is not a Bitx40 repackaged. The Dual J310bi-directional stage configured as a Dual Gate MOSFET has some interesting possibilities. The stage has a manual gain control pot built into the circuit board so that stage gain can be adjusted. This opens up some potential for adding AGC and ALC to this stage so now we can add more additional refinements. One comment I made arising from the Sudden Transceiver fabrication was the opportunity for experimentation. With a change in the BPF and LPF the Simple SSB Transceiver can traverse to other bands. A simple DPDT toggle switch on the front panel could with 1/2 the switch controlling the VFO range and the second half controlling 4 SPDT relays would switch in the proper BPF's and LPF's for each band. One switch, four relays and a few more toroids and caps and you are on two bands.

11 comments:

Great stuff as always Pete. Thanks. I've been thinking about the history of ham radio SSB filters. The mechanical filter you sent me got me thinking. Why was Collins so fond of mechanical filters? Weren't crystal filters available at the time they were pushing mechanical filters? If so, why the prefence? We'll have to talk about this -- and your latest rig -- on the next podcast 73 Bill

I do not know the exact answer for mechanical versus crystal but think the answer lies upstream from the Amateur product lines. As the story goes Collins developed the SSB transmitter/receiver in response to General Curtis LeMay who was looking for long range communications with the SAC Bombers during the early days of the cold war --mid 1950's. LeMay was also a ham so there is a connection there. Once you put gear in a military aircraft that will operate on lengthy missions then the reliability factor of any supplied electronics goes up by a factor of 10. Think about vibration, noise, temperature cycles. internally generated power, lightning strikes, altitude and humidity changes and now the "environmental factors" play a significant role. At that time it may have been a consideration of how well the two approaches would satisfy these concerns. Or something as simple as it was invented and patented by Collins sold to the military and thus eliminated any competition.

I am definitely interested in this project. I have some changes coming up in a few weeks that may allow me to build this unit. Meanwhile, I need to start scrounging parts and ordering a filter, a display and other necessary items.

Thanks for your interest in the Simple SSB. I have started a project page on my website www.n6qw.com. There will be links to the detailed schematics and already I have posted info on the Band Pass Filter and the Low Pass Filter. If you simply unsolder the two 150 PF caps in the BPF and retune the trimmer caps -- it will work on 20M. So you may have an interest in bands other than 40M. If you do an internet search on the W3NQN LPF's you will turn up a document that will serve as a guide to build LPF's for other bands.

Mechanical filters, ie Collins, were available in the early fifties. In the 75A and 51J series receivers, they go from the single crystal phasing type filter to mechanical filters. I think they just predate crystal filters.

As an aside, since they made the filters, they got a good price, which was incentive to stick with mechanical filters.

While early SSB rigs went with very low frequency filters, using LC circuits, I think it was generally phasing rigs, and we saw that when early ssb adapters arrived for receivers, external units using phasing, referred to as "sideband slicers".

Slowly hams started building crystal filters at 455KHz using WWII surplus crystals, lots down around 455KHz and if you weren't lucky Crystal's somewhat lower in frequency that could be ground up.

I don't know why the sequence, I guess enough had to be learned. And it was later that homemade HF crystal filters arrived, maybe just a belief that they were more difficult, maybe just hard fo break from the notion that the IF is lower than the signal frequency.

I don't think there were HF crystal filters commercially available till the late fifties. Maybe they existed, but if so, not yet cheap enough for hams. There was a six meter receiver in QST in 1957 or 58 that used a commercial crystal filter, maybe a Blackhawk?, with an IF at 2 or 5MHz. I think that's one of the first occurances in a homebrew rig.

I can't think of a commercial rig with a lattice filter until after the filters were available to ham. So maybe the Swan single band SSB transceivers came first? No, Heathkit might have been first with one of their Indian named rigs.

When McCoy came along with crystal filters, it was big news, though I'm not sure if they predated hams making 5 or 9MHz crystal lattice filter.

One thing about mechanical filters, they generally had flatter sides, and were symmetrical. Crystal filters often favored one side, at least for a while.

Even today people think they should stick with 455KHz IFs, so the notion of converting up may be too foreign, despite making it much easier to get rid of images, so no need to track stages with the VFO.

Even with homebrew simple receivers, they tended to use 455KHz IFs, until direct conversion made a splash and dimple receivers were generally DC, until ladder filters became popular. After the initial homebrew, if using 9MHz, they'd go with a McCoy or later KVG.

Hi Pete,Just to let you know, I am always interested in all your projects and look forward to seelng them, while I may not build all of them I certainly build some of them,What I can say is that your projects have inspired me and imparted knowledge and confidence. I for one am grateful for your willingness to share that knowledge.Thankyou..........Peter (GW4ZUA)

Hi PeteYes, very interested as always. But as life happens I am always many projects behind. As a result my radios are often "Frankenstein" radios. Little of this radio some of that. HALittle bit of this project, little of that. HaJim wa7hrg